We never thought we'd ever say this, but watching 72-year-old Robert De Niro attempt to have sex is strangely more appealing than seeing Zac Efron's (admittedly perfect) shirtless chest once again.

The totally not-safe-for-work trailer for Dirty Grandpa just dropped, and despite Zac's best efforts at wearing very little, double Oscar winner Robert's sex scene with Parks and Recreation's Aubrey Plaza, 31, has us in stitches.

And the phrase "party until you're pregnant" is all kinds of wrong too.

For more inappropriate bra-tearing, sunscreen squirting and car-humping, watch the trailer above.

Dirty Grandpa hits US cinemas January 22, 2016. An Australian release is yet to be announced.